Net and gross oxygen production from O2/Ar, 17O/16O and 18O/16O ratios

Aquatic Microbial Ecology

Boaz Luz¹  Eugeni Barkan¹ 

关键词: Gross production;    Net production;    Community production;    Oxygen isotopes;    O2/Ar ratio;    Bermuda Atlantic Time-series Study;    Coral reef;   

DOI  :  10.3354/ame01296

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: In aquatic systems, variations in the O₂/Ar ratio and in the ¹⁷O anomaly (¹⁷Δ, calculated from ¹⁷O/¹⁶O and ¹⁸O/¹⁶O) are affected by both physical and biological processes. Laboratory observations suggest that ¹⁷Δ is independent of respiration rate, in contrast to the O₂/Ar ratio. This makes it possible to determine gross O₂ production from measurements of ¹⁷O/¹⁶O and ¹⁸O/¹⁶O of dissolved O₂, while the O₂/Ar ratio can be applied to estimate net O₂ production. We demonstrate how biological and physical forcing modifies the O₂/Ar ratio and ¹⁷Δ during the day and at night in a coral reef near Eilat. This field study confirmed our hypothesis that ¹⁷Δ of dissolved O₂ (¹⁷Δ_dis) is affected by photosynthesis, ocean dynamics and air–water gas exchange, but not by respiration. We also show, for the first time, a detailed record of ¹⁷Δ responses to biological fluxes and subtropical ocean dynamics on a seasonal scale. The measurements were conducted in the Atlantic Ocean near Bermuda during monthly cruises of the Bermuda Atlantic Time-series Study (BATS) from March 2000 to January 2001. With the formation of the seasonal thermocline, ¹⁷Δ_dis significantly increased below the oceanic mixed layer, reflecting the seasonal integration of photosynthesis in the thermocline. Hence, ¹⁷Δ_dis accumulation may be used to calculate the overall rate of photosynthesis below the mixed layer. We used the O₂/Ar ratio and ¹⁷Δ_dis to estimate net and gross O₂ production (NOP and GOP) and directly compared them with production values derived from ¹⁴C incubations. In general, GOP based on ¹⁷Δ_dis was several times greater than production determined via ¹⁴C fixation [P(¹⁴C)], which in turn was somewhat greater than NOP based on the O₂/Ar ratio. The NOP/GOP ratio was 0.08 to 0.21. This implies that the observed high GOP/P(¹⁴C) ratios result mainly from rapid cycling of O₂ between photosynthesis and O₂ uptake mechanisms.

【 授权许可】

Unknown